Fully negative near-zero ultra-flat dispersion photonic crystal fibers in E+S+C+L band

We demonstrate a modified hexagonal three-layer air-hole photonic crystal fiber (PCF) which presents a good ability of dispersion management. The proposed PCF not only achieved an ultra-flattened all-negative dispersion characteristics of 0.15085 ps/(km·nm) fluctuation within the wavelength range of E+S+C+L wavelength band but also has been able to obtain other interesting features such as low confinement loss. Furthermore, the quadrilateral and octagonal structures are investigated to compare the superiority of different structures and analyze why we chose the hexagonal one.